Radio receiving system



MarCh 2, 1937. H, 1 NICHOLS ET AL 2,072,272

RADIO RECEIVING' SYSTEM Filed March 4, 1932 4 Sheets-Sheet 1- F Y z March 2, 1937. vH. J. NICHOLS ET AL RADIO RECEIVING SYSTEM Filed Maron 4, 19s

2 4 Sheets-Sheet 2 March 2, 1937.

H. J. NICHOLS ET A1. v

RADIO RECEIVING SYSTEM Filed March 4, 1952 vvvvvv Marli 2, 1937.

H. J. NICHOLS ET AL RADIO RECEIVING SYSTEM Filed March 4, 1952 4 Sheets-Sheet 4 l of the band pass filter.

Patented Mar. 2, i937 S'ti Are

RADIO RECEIVING SYSTEM (ihio, assignors, by mesne assignments,

Radio Corporation of America, New York, N. Y., a corporation of Delaware Application March 4, 1932, Serial No. 596,732

6 Claims.

This invention relates to universal remote control unit for radio receivers and has for an object to provide a eXibly attached device to be used in conjunction with any radio wave translating device whereby the same may be controlled fully in accordance with the desires of anattendant.

Another object of the present device is to provide a remote control unit that will improve the radio reception. This has been accomplished by adding a device to a receiver that incorporates selective devices or circuits and the heterodyne principle.

Another object of this invention is to improve the sensitivity ci a radio receiver` This may be accomplished by the signal amplilication gained in the remote control unit.

Another object of this invention is to provide selective means at the remote control unit that limit the output to the selected signal and reduce the image response. This has been accomplished by providing a signal utilization device in the remote control unit.

Another object of this invention is to utilize the incoming signal at the remote control unit to produce a resultant wave oi different frequency for amplification. This has been accomplished by mounting an oscillator in the remote control unit whose product combines with the incoming signal to form a beat frequency.

Another object oi this invention is to provide a control mechanism in a remote control unit that tunes a band pass iilter and actuates an adjustable device of an oscillator so that the kfrequency of a beat signal is constant regardless of the setting This has been accomplished by actuating the tuning devices in the band pass lter simultaneously with the adjustable device in the oscillator.

Another object of this invention is to use a radio receiver, having its tuning devices set at a predetermined position, in conjunction with a remote controller for receiving any one signal within the range of the tuning device of the remote control unit, without the need of thereafter f' changing the tuning devices on the said radio receiver. This has been accomplished by mixing the incoming signal with another wave to produce a resultant that is transmitted to and reproduced by the receiver.

Another object of this invention is to provide means for producing in the remote control and means for eiiiciently transmitting between the remote control and receiver, signal energy having a predetermined fundamental frequency. This may be accomplished by providing simultaneous tuning of an oscillator and selective means in the remote control and tuning the transmission line to be efficient at the frequency of the resultant signal.

Another object of this invention is to provide means for iiexibly attaching a movable control unit to any radio reproducing device. This may be accomplished through the use of properly constructed wire connections.

Another object oi this invention is to provide means for remotely controlling a radio receiver that does not radiate energy or pick up stray signals or noises within itself. This may be accomplished through the `proper construction and shielding of the unit and the transmission cable.

Another object oi this invention is to prevent distortion of the output signal caused by disturbing signals being impressed upon the incoming signal and the signal transmitted from the remote control unit to the radio receiver. This has been accomplished by shielding the appropriate leads.

Another object of this invention is to provide means for tuning the transmission line in such a Way that it will be most eliicient at some predetermined frequency. This may be. accomplished as disclosed by utilizing the capacity between the shield and line and other capacity in such a Way that the whole output circuit is tuned to the desired frequency value.

Another object of this invention is to provide a transmission line together with suitable matching devices that will not appreciably attenuate the signal voltage impressed upon the remote control unit. This has been accomplished by providing a transformer or impedance matching device that matches the impedance of the antenna with the impedance of the line at some desired frequency and using a second impedance matching device to condition the signal received to be used by a translation device.

Another object oi this invention is to provide means in the remote control unit so that the advantages of the heterodyne principle of reception may be applicable to tuned radio irequency receivers and the advantages of two intermediate irequencies applicable to superheterodyne receivers. This may be accomplished as herein disclosed by incorporating an oscillator and detector in the remote control unit.

Another object of this invention is to provide means for lighting the tubes and an illuminating device in the remote control unit. This has been accomplished by providing a transformer in the remote control unit energized from the regular source of lighting circuit.

Another object of this invention is to provide means for a dual control, so that the energy output of the radio receiver may be controlled at the remote unit. This has been accomplished by providing a volume control in the remote control unit that controls the output of the radio receiver.

Another object of this invention is to provide means for controlling the output of the receiver as well as the signal response frequency from the remote control unit. This may be accomplished by providing a suitable control in the remote unit for the output of the receiver.

Another object of this invention is to provide a switching mechanism whereby the antenna may be connected either to the radio receiver or to the remote control unit. This has been accomplished by providing a switch that connects the antenna to the input terminals of the radio receiver in one position and that connects the antenna to the remote control unit in another position.

Another object of this invention is to utilize the antenna that supplies the signal to the radio receiver whereby a separate antenna need not be provided for the remote control unit. By so doing it is possible to use the antenna circuit either for the radio receiver without the remote control or with the remote control.

Another object of this invention is to provide a remote control which is capable of making possible the reception of signals outside of the ordinary broadcast band, with a receiver built for use within the broadcast band range only. This may be accomplished by the use of interchangeable coils for use in the control unit.

Further objects and advantages of the present invention will be apparent from the following description, reference being had to the accompanying drawings wherein a preferred embodiment of one form of the present invention is clearly shown.

In the drawings:

Fig. 1 discloses a remote control unit attached to any radio receiver of conventional design.

Fig. 2 discloses a plan View of the remote control unit casing.

Fig. 3 is a bottom plan view of the remote control base.

Fig. l is a detail view of a remote control cable.

Fig. 5 is a sectional view thereof.

Fig. 6 discloses a schematic wiring diagram of the circuit arrangement used in the remote control unit and its connections to one type of a standard receiver.

Fig. '7 discloses a similar diagram of the circuit and its connection to another type of receiver.

Fig. 8 discloses a modified form of the remote control unit, embodying a modification in the voliune control means, and additional selective and amplifying means.

With particular reference to the drawings, Fig. 1 illustrates the physical embodiment of the remote control device and its adaptation to one type of receiver. Here the remote control unit if; is connected by a suitable cable 32 with the radio instrument or other wave translation device l2, which houses any suitable radio receiver and that may embody either of the receiver circuits illustrated in Figs. 6 and '7 or any modication thereof. For purpose of illustration the receiver circuit is indicated at I3 and presupposedly is provided with the necessary stages of detection and amplincation I5, as well as a power pack or transformer I'I and whose signal output is made use of by a loud speaker, reproducer or equivalent device I9. Since the type of receiving circuit with which the remote control unit is to be used is substantially incidental, except as set out in a later paragraph, it is not believed necessary to go further into description of the same except as will hereinafter follow where reference will be made to the detail application of the remote control unit with the said receivers.

However, the detailed depicting of different circuits in Figs. 6, 7, and 8 have their application to illustrate the universal adaptation of the remote control unit to any desired type of receiver. With this explanation suice it to say that the receiving circuit illustrated in Fig. 6 is designed to illustrate the adaptation of a remote control unit to a receiver tted with manual control for the receiver output, while Fig. 7 is illustrative of an adaptation to a receiver having automatic control for the receiver output. On the other hand, Fig. 8 is illustrative of a remote control unit embodying a volume control tube.

The remote control unit I9 disclosed may be used with practically any modern or proposed radio receiver I2 which may be a tuned radio frequency receiver, a superhet-erodyne receiver, a super-regenerative receiver or the like. However, instead of using a radio receiver provided with selective tuning devices, a receiver having its elements secured at a xed setting may be constructed for use in connection with the remote control unit and can be used as will presently appear. As disclosed in the drawings a casing i4 is provided, within which is housed a detector i5, an oscillator I8 and an appropriate circuit incidental thereto. The particular circuit adopted is that illustrated in Fig. G or i', and is ei:- plained as follows. The numeral 2E) is indicative of an antenna which is usually connected to the receiver I3. Provision is made for connecting the antenna with a transformer 22, and it is desired to incorporate a switching mechanism 24 in this connection for purposes, and the structure of which will presently appear.

The transformer 22 is preferably a step-down transformer whose purpose it is to match the impedance of the antenna to that of the line at or near the high frequency end of the band of signals to be received. The primary winding 2E of the transformer 22 is connected in the antenna circuit and grounded at 28. The transformer 22 is preferably located near the aerial post in the radio receiver so as to have a more or less direct connection with the said antenna. The secondary winding 3B of the transformer 22 has one terminal grounded at 28 and the other terminal connected to a lead 3| located within a cable 32 shown in Fig. 1, communicating with the remote unit. The lead 3| is an insulated conductor and is shielded by a metallic shield 33 having its ends grounded at 28 and 34, so that no stray impulse is picked up by the lead 3l as the signal is transferred from the transformer 22 to a transformer 36. The transformer 36 has its primary 38 connected in series with the lead 3| and is grounded at 34. Since the transformer 22 matches the impedance of the antenna to that of the line preferably at or near the high frequency end of the band, the transformer 35 matches the impedance of the line to that of the input circuit of the remote control, preferably at or near the low frequency end of the band of signals to be received. It is understood, however, that the points of matching the impedances might be reversed or shifted and still come within the spirit of the invention. The description set forth h-ere is merely an example of a method of obtaining uniform signal attenuation over the range of frequencies to be received, and also to obtain loW losses.

Another method of accomplishing the same advantage of uniform signal attenuation and low losses over the range of frequencies to be received, is to match the impedances at the same and preferably at or near the low frequency end of the band, and then to use a lo-W impedance input circuit at the remote unit. In other Words, the impedances matched by transformers 22 and 36 -are matched at a loW frequency and the impedance of coil i2 of the transformer 44 is made low.

The secondary Winding 40 of the transformer 3&5 has one terminal grounded at Sill and the other terminal connected tothe primary Winding 42 of a transformer i4 that is also grounded at 34. This transformer is provided With a secondary winding lit and is connected in parallel with a tuning condenser dit, and a fixed mutual condenser 5l) to form a closed resonant loop. At a point intermediate the terminals of the elements llt and 5i), the loop is grounded at 52. An inductance 56 and a variable condenser 58 together with the mutual condenser 5U forms a second resonant loop and cooperates With the rst loop that includes the inductance i6 and the condensers 48 and '5t to form a band pass filter 6G, and which has a double peaked resonant curve Whenever a proper value is selected for the mutual condenser Eil. At a point intermediate the condensers 5t and 5c connections are also made to ground at 52 and from this same or similar intermediate point a resistance 64 is inserted and connected across the condenser 5t! so as to be in series With the inductance 56 and ground.

The output of the band pass iilter t8 is connected to a grid E52 of the detector I6, so that the direct current path of the grid circuit extends from the grid 62 through the inductance 56 and through the resistance tt that is also grounded at 52. As the resistor 6ft has a very high resistance l*as compared to the condenser 5t, the resistance Sli does not materially influence the shape of the resonance curve of the band pass lter St. The signals selected by the band pass iilter t@ are combined with locally generated oscillations produced by a device to be described, so that the radio frequency signal passing from the detector it through a lead l@ to the input terrnirial H of the radio receiver |3 is of different frequency from the incoming signal.

The device for producing the locally generated oscillations, includes an oscillating tube i8 having its grid l2 connected at an intermediate point "lli of an inductance l, through a condenser i3 connected in series With a resistance Si). An adinstable condenser 82 and a variable condenser .gli are connected together in series, and thence are connected in parallel with the inductance i6, to form a resonant circuit inductively coupled to a coil tt in the plate circuit of the oscillator I8, and also inductively coupled to a coil 83 located in the circuit of the detector cathode 9d that is grounded through a resistance 92 at Slt. The resistance Q2 supplies a bias to the cathode 9@ of the detector it, and the by-pass condenser 96 forms an alternating current path shunted about the biasing resistance 92.

Returning to the oscillator i8, its cathode Iii@ is connected to one terminal of the resonant circuit including the inductance 16 connected in parallel with the condensers 82 and E@ and grounded at m2. A grid leak resistor |64 has been connected intermediate the grid l2 and the cathode me. From this it can be readily seen that as oscillations are set up in the oscillator, including the tube I8, that these oscillations will be transferred to the cathode @En of the detecte-r l5, so as to' combine with the incoming signal to form a beat signal having a frequency that is either the sum of or the difference of the incoming signal and the locally 'generated oscillations.

A plate or B potential is supplied to the plate H0 of the detector it by the B source from the radio receiver through a lead H2 carried by the cable 32 and through an inductance lit. The lead ||2 also supplies a B potential to the plate il@ of the oscillator I8, and to the screen |20 of the detector It, through the resistance H8. The resistance of the inductance in series with plate lit is so low that the potentials on the plate H5 and the screen |29 are substantially equal. Condensers |22 and |25 have their terminals connected intermediate the plate circuit and the screen grid circuit and are grounded at @i5 to provide by-pass circuits for the alternating current component.

As far as possible it is desirable to control the volume output of the receiver at the remote unit so that no adjustment will be required of the volume output at the radio receiver. This may be accomplished in diverse Ways but the preferred for l of volume control for this purpose as disclosed in Figs. 6 and '7, includes a. resistor 35 having one terminal connected intermediate the high potential terminal of the secondary Winding @D of the transformer 36, and the high potential terminal of the primary Winding i2 of the transformer 44. An adjustable tap I3?. short circuits a part of the resistance I3@ and is grounded at M2 so as to form a by-pass circuit for a portion of the signal if it is desirable to reduce the magnitude of the incoming signal. Thereby the volume of the signal may be controlled by adjusting the tap |32 on the resistor i3d. A lead |34 from the resistor |33 may, if it is found necessary, be connected to a suitable volume control in the radio receiver as illustrated in Fig. 6.

In addition to the volume control already described, another volume control mounted for operation by the same control knob |35 may be used to control the potential supplied to certain other grids, or other elements in the radio receiver, depending upon the particular design of the radio receiver used. This volume control ini,

cludes a resistor Mil having one terminal grounded at |42 and a lead |43 for connection to the receiver. An adjustable tap Iliffmay be adjusted along the resistor MB to change the bias supplied to certain control elements found Within the radio receiver, a lead its with the lead l it providing for that connection. The detailed circuit of the volume control in the radio receiver may be connected in either instance as illustrated.y

The remote control unit thus provides a dual volume control such that the unit may be adapted to practically any type of radio receiving device, Whether the receiver be one fitted with only a manual control for the volume output or Whether the receiver incorporates means for automatic volume control. The adaptation of the remote unit to a receiver of the first type is fully illustrated in Fig. 6 where the lead i134 from the resistor |38 makes connection with thevolume control 2l4 of the receiver substantially as will be described in a later paragraph with respect to the multiple circuit switching mechanism. t will be noted that the volume control means provided by the remote unit is substantially divided in half, the rst portion |30 of which is designed to be connected into the receiver circuit as Will presently appear, while the second portion |40 may be connected into a receiver providing for automatic volume control as illustrated in Fig. '7.

In the latter instance, or where the set is provided with an automatic volume control, onehalf of the dual control of the remote unit is connected in the circuit of the receiver preferably by carrying the lead |43 to one terminal |45 of the secondary in the reproducer device 9, and by disconnecting the lead joining the voice coil, usually connected to the said secondary at this point, and joining it to the lead |46 communicating with the adjustable tap |44 on the resistor |40. For best results, the other lead joining the secondary of the device i9 and its voice coil should be provided with a ground connection as at |4l. It may also be found desirable to disconnect the portion |39 of the volume control in the remote unit, which may be accomplished by severing the lead |49, substantially as indicate-d at |5|. In either instance, that is to say, whatever adaptation of connection between the remote unit and the receiver is made, means are provided for fully controlling the volume output of the receiver from the remote unit, and the volume control in the remote unit is superimposed Iupon that contained in the receiver and makes for complete control thereover.

Still another modication of the volume control which may be applied to the remote control unit is disclosed in Fig. 3. As will be apparent from the following description, this form of control in addition to giving the desired volume control also adds additional amplificati-on to the remote unit as Well as additional selective means to the system. Since the detector and oscillator circuits of this modification are essentially the same as those previously disclosed simil-ar reference numerals have been applied to the parts in this modication.

The plate H0 of the detector i6 is coupled to the input of a therrnionic tube l5 through a tuned transformer 6 l. The potential on the plate H0 of the tube |S is supplied through a primary 63 of the transformer 6| from the receiver unit through lead H2. The primary 63 is tuned by a condenser 65 to be resonant at the intermediate frequency. Resistors 69 and 1|, which are in series and connected at one end to lead H2 and grounded at the other end at i3, form a voltage divider which supplies the potential to the screen grid l2?! through its connection to the common terminals of the resistors. The condensers |24 and |22 connected to the screen grid |29 and lead H2 respectively, and ground at their common terminal at |26, form high frequency bypasses for those circuits. A secondary 6l of the transformer 5| has one end connected to a grid 'F9 of the tube l5 and its other end grounded at 8|. A condenser 'il tunes the secondary @l to resonance at the intermediate frequency. The potential on a screen grid of the tube 'l5 is supplied from the common terminals of resistors B9 and ll, and the potential on a plate S3 of the same tube is supplied from the lead H2 through the choke coil I4. The heater-lighting potential is supplied from the transformer secondary |58 as for the other tubes. A resistor 8l is connected in series with a cathode of the tube 15 and establishes the minimum bias to that tube and is also in series with the volume control |30 having the movable contact |32 and grounded at |42. Hence by varying the position of the movable contact |32 of the Volume control |30 the bias on the grid of the tube 'l5 is varied. That is, the greater the resistance between the end of the resistor Sl and the movable contact |32 the more negative the bias of the tube. Since one end of the Volume control |35 is also connected by the lead |49 to a point intermediate the coil 40 and coil 42, that control serves a dual purpose. At the same time as the bias on tube l5 is increased, which tends to reduce the volume, the signal input to the unit is decreased by the decrease in resistance across the signal input circuit. Thus the two controls are complementary. A condenser 89 connected to the cathode 95 and grounded at 9| forms a bypass for the bias resistor 8l and volume control |35. Plate |33 of tube l5 is connected with the receiver through the condenser |54 and the shielded line lil, which transfers the signal to the receiver unit, as previously described.

It may now be seen that addition of the transformers Si and tube l5 tothe remote control unit, give additional ampliiication to the unit and adds additional selective means, since the signal in the plate circuit of the tube i6 has a predetermined frequency value and the transformer 6| is tuned to resonance at that frequency. It transfers the signal to the grid 'i9 of tube 'l5 at its point of maximum eiciency.

rEhen the signal in the plate circuit of the tube "i5 has the same fundamental frequency as that in the plate circuit of the detector I6. The line 'l0 may be tuned by the condensers |54 so that maximum voltage is developed between the lead 'dll and the shield |52 which surrounds it. Since it is the voltage between lead 'Ill and the shield E52 which is applied to the input of the receiver, the tuning of that line by the condenser |54 makes that voltage transfer between the remote unit and the receiver more eiiicient. This modification may preferably be used with the receiver unit, such as that shown in Fig. 6, but may very well be used with the receivers of the type shown in Fig. 7.

The structure thus far described is substantially that enclosed within the casing I4 of the remote control unit |6 illustrated in Fig. l. The unit also houses a transformer |59 that is conveniently mounted in the base thereof as indicated in Figs. 1 and 3, and has its primary winding |52 connected by appropriate leads |54 and 56 included in the multi-conductor cable 32 from whence they make connection with a series plug |53. At an appropriate point |69 in the conductor |54 there is provided a contact terminal, and a switch |52 that optionally contacts therewith and joins a terminal |64 connected to a third lead |66 that also has communication with the series plug |58 as will presently appear. rThe secondary |68 of the transformer |50 is provided with conductors l'll and lf2 to which connection is made with the laments |74 of the detector and llt of the oscillator for lighting the same. Inasmuch as there are many lines in the drawings it is deemed sufficient to make this statement without showing the actual connection in both circuits, believing it to be obvious to one skilled in the art how these connections may be made simply by referring to Fig. 7. A dial light |18 is oonnected across the leads |10 and |72 and in series with an appropriate resistor |85. One terminal of the secondary l has connected thereto a conductor H22 that joins the shield H52 of the conductor lll and is eventually grounded at E56. The structure thus far described constitutes the essential portions of the remote control unit according to the adaptation that has been made, and when reference is had to Fig. 6 ofthe drawings it will be seen that it is in main all of that structure to the left hand side of the terminal `l0 strip indicated at E85 and shown in dashed lines.

For convenience it may be regarded that the terminal strip i8@ is indicative of the content of the multi-conductor cable 32 which carries some '7 or 8 leads or conductors providing the various communications between the remote unit and the receiver to which it is to be attached, all of the receiver structure being indicated as having its various connections coming in from the right hand side of the terminal strip |86. Inasmuch as the remote unit is designed for universal adaptation to practically any type of radio receiver, and since it may be desirable in some instances to control the receiver without the remote unit, provision is therefore made for accomplishing those results, which, it is believed are fully illustrated in the circuit diagram in Fig. 5. The universal adaptation of the remote unit to that type of receiver is illustrated by example in Figs. 6 and '7 though it will be obvious to one Skilled in the art that the remote unit may be connected into the circuits of other receivers than the two particular types illustrated. To save confusion of illustration and so as to make use of as few lines as possible the pron visions for using the receiver without the remote control unit has been illustrated only in Fig. 6, it being obvious to one skilled in the art that the same principles can be, or are to be observed when this feature is applied to any other receiver than that illustrated in Fig. 6.

In illustration of the latter feature, a multicircuit controlling switch is provided and for purpose of illustration may include the shiftable Contact members Het, 92, and 191i that cooperate 15 with contact members |98, 20u, 204, and 236 respectively, the movable elements being manually and coincidentally operable by a knob or button 2lb fixed upon a common shaft or operating member M2 indicated by dot-and-dash 50 lines. ln further explanation of this switch it will be observed that the movable element le@ is join-ed to the lead-in wire from the antenna 2@ and is movable from a position to engage the contact 8% to a position in which it engages 55 the contact 204i, and likewise the movable element E92 is moved from a position engaging the contact Zilli to a circuit open position. Also the movable element les is engageable with either of the contacts 26d or 2M so as to make the proper 60 changes in the circuit with regard to the volume control of the receiver. By this structure diagrammatically illustrated, the attendant is permitted by manipulation of the knob 2m to connect in the remote unit so as to fully control the 65 receiver, or he may entirely sever that unit in its operative connection with respect to the receiver. The full line position of the movable elements of the switch indicates, the connections when the remote unit is to act as a controller 70 for the receiver, while the dotted line position indicates the connections that are made when the receiver is to be used without the remote unit.

When the remote unit is to be used in conrE75 nection with a radio receiver such as appears by the full line position of the multi-circuit switch illustrated in Fig. 6, the antenna 2li is then connected through the movable element i9@ with the Contact H98 from whence the incoming signal picked up by the antenna E@ passes through the transformer 22 and thence is impressed upon the signal utilization device of the remote unit, from which the conductor 'it returns the signal output and by reason of its connection with the movable element 92 in engagement with the contact 2li@ impresses the signal upon the input terminal Il of the receiver l5. The volume control element i3@ has connection by its lead iStl, and the movable element iet that is then in engagement with the contact 2M, with the volume control element 2id contained within the receiver by which the audible output of the receiver is controlled.

With the connections thus made, and with the series plug 58 attached to the source, and with the plug 22B of the power unit il properly attached and with the instrument control switch 222 and the remote control switch lf2 being closed, the remotev unit and receiver are in proper hook-up to provide for complete control of the receiver i3 by the remote unit it.

When it is desired to use the receiver without the remote unit the multi-circuit switch is moved to the dotted line position in which all of the essential connections between the remote unit and the receiver are severed, and in which the antenna 2@ is directly connected with the input terminal ll of the receiver by reason of the movable element ld engaging the contact 2G@ and the movable element i9@ being in engagement with the contact 266, wherebythe proper ground connection is made from the volume control 2M to ground at 22d. It will be noted that in this dotted line position the connection over the lead Til, from the plate of the detector to the terminal 'il of the receiver is open circuited, thus disqualifying the signal output of the remote unit. Opening of these circuits will not wholly deenergize the transformer l5@ and will not affect the source of energy impressed upon the power unit Il?, inasmuch as the series plug E58 has provision by means of the switch E62 for complet ing the circuit through the said power unit from the elements 2lb and 2 i8 irrespective of the open or closed condition of the said switch. While this will cause the filaments of the remote unit to still hum, it may be overcome if objectionable by withdrawing the series plug 553 from the source and inserting the plug 22@ in its place.

When the remote control unit is used in connection with a radio receiver having tuning de vices, those devices are set in some predetermined position, as for example to a wave length somewhat outside of the usual broadcast range, or even to a wave length within the range that is relatively spaced from other waves in the assignment of stations.

It is preferred, however, to tune the receiver to a point just beyond the low frequency end of the broadcast band. say 535 kilocycles. When the receiver is tuned to that frequency the oscillator will track the first detector tuning in the remote control unit. and the dial thereof will read correctly in frequency. It is obvious, that when the receiver has its tuning devices set at some other point on the band, that the remote unit may be constructed or adjusted to operate most eiciently at that predetermined receiver setting.

The remote control unit as here disclosed contains a band pass filter used as a station selector,

with an oscillator |8 and a detector I6. Either a separate oscillator and detector, or a single tube oscillator and detector may be used, so that a heat frequency can be produced by combining the desired incoming signals with locally generated oscillations equal to the frequency for which the receiver is set. The incoming signals may be signals within the usual broadcast range of the radio receiver, or signals outside of the usual broadcast range generally referred to as short Wave signals. In the latter instance the remote control unit can of course be provided with interchangeable coils, so as to change its range from the usual broadcast range to the short wave range, and vice versa.

To accomplish the greatest efficiency of the apparatus at least two of the leads contributing to the cable 32 communicating between the receiver and the remote unit are provided with metallic shields. One of these is lead 3| that is enclosed in its shield 33, one end of which is grounded at 34 by means of an appropriate connection |84, and the other end of which may metallically join a shield 233 disposed about the transformer 22, which may have its ground connection completed by a lead 232 from the ground 28 in communication with the shield 33, or else the shield 230, and this grounding may be made more certain by extending the lead 232 with a lead 234 having communication with a ground post 235 provided by the receiver. Likewise the lead 'lli extending from the plate I I0 through the condenser |54 is provided with a shield |52 and grounded at |56. All of the ground connections found in the remote control unit are grounded to the remote control casing lll substantially as indicated, and which in turn may be connected by a ground wire to the ground terminal of the radio receiver.

The operation is believed to be obvious from the structure that has been heretofore described, and it is thought to be apparent that when the remote unit is attached to the receiver that the entire control of the receiver, whether it be tuning control or volume control, may be accomplished from the remote unit. The remote unit being flexibly attached to the receiver makes provision for using practically any type of receiver whether it be one of the tunable type or one of xed setting, which receiver may be stowed away in any convenient or available space and operated without further attention being given to it than merely to manipulate the remote unit.

The mechanism within the remote unit provides selective means for limiting the output of a selected signal and reduces the image response through the operation of the signal utilization device. By mounting the oscillator in the remote unit and combining its product with the incoming signal there is produced a wave of different frequency in the form of a beat frequency, which when transmitted to the receiver may be amplifled. This is accomplished by controlling in unison the tuning of the band pass lter and the oscillator device, Thus signal energy produced in the remote unit is then transmitted to the receiver through an appropriate transmission line.

The line joining the remote control with the receiver is so constructed by shielding both the unit and the transmission cable that there will be no radiation of energy, nor will there be any pick-up of stray signals and other noises. The shielding of the leads also prevents distortion of the signal put out over the line "lll, and the tuning of this out put-lead makes for the greatest elllciency at a predetermined frequency. This in main is accomplished by the trimmer condenser |54, by which the capacity existing between the shield and line is controlled and may operate to tune the line to the desired frequency value. By incorporating the line matching devices, that is to say, the transformers 22 and 36, the signal voltage impressed upon the remote unit will not be objectionably attenuated, and by interposing one of the line matching devices between the antenna and the receiver, the need for providing a separate antenna for the remote unit is obviated. The multi-circuit switch inserted in the disclosure of Fig. 6 provides for this dual use of a single antenna as well as permitting the use of the receiver either with or without the remote unit.

It will be further noted that adaptation is made of the superheterodyne principle, particularly in the instance where the adaptation is made as depicted in Fig. 6, due to the incorporation of an oscillator and the detector in the remote control unit, for in fact the remote unit may be considered as a superheterodyne converter. Provision is therefore made for controlling from a remote point a receiver having its tuning devices set at some predetermined position. The detector and oscillator within the remote unit provide for the mixing of the incoming signal with another wave to produce a resultant that is transmitted to and reproduced by the receiver, and these two devices with perhaps also the tuning device of the remote unit in effect add just so much to the standard receiver and thereby operate to improve the radio reception. Due to the signal amplification gained in the remote unit the sensitivity of the receiver is also improved.

While the form of embodiment of the present invention is herein disclosed, constitutes a preferred form, it is to be understood that other forms might be adopted, all coming within tho scope of the claims which follow.

What is claimed is as follows:

1. A system for receiving broadcast signals transmitted within a band of frequencies, saidl system including a radio receiver having an antenna, said receiver having a selective input resonant to a frequency below the broadcast range, a remote control unit, means for transmitting all of the incoming signals received by the antenna. to the remote control unit, said means comprising a transmission line electrically connected between the antenna and the remote control unit through means acting to match substantially the impedance of the antenna to theimpedance of the line in the vicinity of one end of the band of frequencies to be received, means at the remote control unit for selecting a predetermined signal for amplification, a device in the remote control unit for changing the frequency of the selected signal to a xed frequency equal to said rst frequency, and means for transmitting the fixed frequency signal to the radio receiver, whereby the radio receiver amplies such predetermined fixed frequency.

2. A system for receiving broadcast signals transmitted Within a band of frequencies, said system including, a radio receiver having an antenna, said receiver having a selective input xedly resonant to a frequency below 550 kilocycles, a remote control unit, means for transmitting the incoming signal from the antenna to the remote control unit, said means comprising a transmission line, one end of which is electrically connected to the antenna through means.

acting substantially to match the impedance of the antenna to the impedance of the transmission line in the vicinity of one end of the band of frequencies to be received, the other end of the transmission line being electrically connected to the input circuit of the remote control unit through means acting to substantially match the impedance of the line to the impedance of the input circuit of the remote control unit in the vicinity of the other end of the band of frequencies to be received, means in the remote control unit for changing the incoming signal to a signal having a frequency equal to said rst frequency, and means for transmitting said changed frequency signal from the remote control unit to the radio receiver.

3. A remote control unit for a radio receiver comprising in combination, a detector having its plate circuit connected to the input terminal of said radio receiver, an oscillator for generating oscillations of a desired frequency range, means extending from the aerial of the radio receiver to the detector for impressing the incoming signals upon the detector, said means comprising a transmission line, one end of Which is electrically connected to the antenna through means acting substantially to match the impedance of the antenna to the impedance of the transmission line in the vicinity cf one end of the band of frequencies to be received, the other end of the transmission line being electrically connected to the input circuit of the remote control unit through means acting to substantially match the impedance of the line to the impedance of the input circuit of the remote control unit in the vicinity of the other end of the band of frequencies to be received, and means for impressing the locally generated oscillations upon the detector, said oscillator and signal frequency ranges being such that a beat frequency of the order of 535 kilocycles is transmitted from the detector plate circuit to the input terminal of the radio receiver.

Ll. A remote control unit for a radio receiver comprising in combination, a detector having its plate circuit connected to the input terminals of said radio receiver, an oscillator for generatingr oscillations, a high frequency conductive path extending from the antenna of the radio receiver to the detector for impressing the incoming signals upon the detector, said means comprising a transmission line, one end of `which is electrically connected to the antenna through means acting substantially to match the impedance of the antenna to the impedance of the transmission line in the vicinity of one end of the band of frequencies to be received, the other end of the transmission line being electrically connected to the input circuit of the remote control unit through means acting to substantially match the impedance of the line to the impedance of the input circuit of the remote control unit in the Vicinity of the other end of the band of frequencies to be received, means for vimpressing the locally generated oscillations upon the detector, whereby a beat frequency is produced, and means for transmitting the beat frequency to the radio receiver including a tunable amplifier element for improving the efficiency at a predetermined frequency.

5. Radio receiving apparatus comprising a plurality of units, one of said units including amplifying, detecting and reproducing means, another unit having tuning means, an oscillator, a non-oscillating detector, and an amplier, means providing bias for the ampliiier, a cable connecting said units and including one or more shielded leads, and means tuning one of said leads to be eilicient at a predetermined frequency, said amplifier having means for limiting the bias to a predetermined minimum value and means for varying the bias negatively from that minimum value, said bias variations serving to control the signal volume transmitted between the units by the cable.

6. A system for receiving broadcast signals, said system including a radio receiver having an antenna, the receiver having a selective input resonant to a frequency below the broadcast range,

a remote control unit for the receiver, means for transmitting all of the incoming signals received by the antenna to the remote control unit, said means comprising a transmission line, one end of which is electrically connected to the antenna through means acting substantially to match the impedance of the antenna to the impedance of the transmission line in the vicinity of one end of the band of frequencies to be received, the other end of the transmission line being electrically connected to the input circuit of the remote control unit through means acting to substantially match the impedance of the line to the impedance of the input circuit of the remote control unit in the vicinity of the other end of the band of frequencies to be received, means at the remote control unit for selecting a predetermined signal of the broadcast range for amplification, a frequency changer device in the remote control unit for changing the frequency of the selected signal to a fixed frequency equal to the first-named frequency, means for transmitting the said fixed frequency signal energy to said radio receiver whereby the radio receiver amplines said fixed frequency, and said receiver including a detector for demodulating the amplied fixed frequency.

HARRY J. NICHOLS. HENRY C. FORBES. WALTER S. HARMON. HOMER J. LOFTIS. 

